James thorne and ebenezer banton burr



(MM) JQTHORNE & E. B. BURR.

LENS FOR SIGNAL OR OTHER LAMPS.

No. 446,304. Patented Feb. 10,1891.

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UNITED STATES P TENT OFFICE.

JAMES THORNE AND EBENEZER BANTON BURR, OF LONDON, ENGLAND; SAID BURR ASSIGNOR TO SAID THORNE.

LENS' FOR SIGNAL. OR OTHER LAMPS.

SPECIFICATION forming part of' Letters Patent No. 446,304, dated February 10,1891.

Original application filed July 2, 1888,

297,642. (ModeL) Patented in England February 12, 1887,

June 8,1888, No, 189,824.

Serial No. 278,744. Divided and this application filed January 26, 1889. Serial No.

Nox 2,262; in Belgium April 30, 1888, No. 81,377, and inFrance To all whom it may concern:

Be it known that we, JAMES THORNE, merchant, and EBENEZER BAnToN BURR, engineer, subjects of the Queen of Great Britain, and both residents of London, England, have invented a new and useful Improvement in Lenses for Signal and other Lamps, (for which we have obtained patents in Great Britain, No. 2,262, dated February 12, 1887; in France, No. 189,824, dated June 8, 1888, and in Belgium, No. 81,377, dated April 30. 1888,) of

which the following is a specification.

or may not be such as is described'in our.

application filedJ uly 2, 1888, Serial No. 278,744,, of which the present application isa division.

Heretofore spherical lenses have usually been employed with reflectors for the purpose of concentrating the rays from a source of light-for example, in the signal-lamps for railway and other purposes. In some i11- stances parabolic reflectors have been used,

. generally without a lens, asin the well-known projectors or search-lights, though sometimes with a lens of spherical form. Moreover, it has heretofore always been considered necessary that in order to increase the illu minating power of a lamp a lens should be used in combination with a reflector. Now we have discovered that by employing a solid lens A, of which the interior surface B is plane and the exterior surface O is so curved in one sweep as to give an approximately parallel beam from a point we can without a reflector attain results in respect of the concentration of the rays and the intensity of the projected beam which exceed the results heretofore attained in these respects with the ordinary spherical lenses and reflectors. The curvature of the exteriorsurface O of thelens should for this purpose be parabolic or in the form of a paraboloid.

In carrying out ourinvention,therefore, we dispense with a reflector and use a single lens, of which the interior surface B isplane, and the exterior surface 0 of which has the form of a paraboloid, as above described, so

that the said lens will utilize all or nearly all the available rays emanating from the source of light that is to say, will convert these rays into an approximately parallel beam. The said lens is placed at a greater or less distance from the light, according to the dimensions of the lens. Moreover, in a lamp provided with an improved lens, as above described, instead of the shape of light or flame of the lamp bein gvisible through the lens, asin lamps heretofore constructed,the lens presents the appearance of an illumined disk, the light having substantially the same brilliancy over the entire area of the lens, and the lamp throws out a beam of intense light, which can be seen at a .great distance from the lamp. We thus obtain much better results than heretofore with respect to the intensity of the beam projected from the lamp.

Our improvements are applicable to all kinds of lamps which require lenses or reflectors, Whether oil, gas, electricity, or other illuminating agent be used therein. It will thus be seen that we are enabled to replace the parabolic reflector used in the well-known search-light by a parabolic lens that is much more easily kept clean and performs precisely the same function. Moreover, a lamp provided with the parabolic lens instead of a reflector is capable of having alens placed on each side, and may in this way be used as a railway signal-lam p in both directions.

It will be understood that with the source of light placed at a fixed distance from the lens the concentration of therays is regulated by the curvature of the parabolic surface. Thus the more nearly it is desired to bring the rays to a parallel beam the greater must be the curvature of the parabolic surface. 2. A lamp Haring noreflector and provided From this it; Willalso be understood that any with a solid lens of plano-para-bolic form which variation in the distance between the source will project the light in one approximately of light and the lens can also be compensated parallel beam, substantially as described. 5 for by varyin the curvature of the lens. r

VVha-t We 01311111 is' JAMES HIORNE' 1. A lamp provided with a solid lens, one EBENEZER BANTON BURR' surface of which is flat or plane and the other \Vitnesses: surface of whichis a paraboloid,substantially DAVID YOUNG,

10 as described. A. E. NIXON. 

